Many chemical reactors use vertical tubes which are filled to a desired elevation with catalyst. There typically is an empty space between the top of the catalyst and the top of the reactor tube, which is known as the outage. The elevation of the top of the catalyst is often referred to as the outage level. In order to ensure that the level of catalyst is uniform throughout the tubes, it is common to vacuum catalyst out of those tubes in which the outage level is too high. However, this vacuuming often jostles, breaks, and otherwise damages or diminishes the catalyst. It also has been difficult and time consuming to ensure that the catalyst is vacuumed to the correct outage level in every reactor tube. Vacuuming also may be used to clean out the chemical reactor tubes before loading them with new catalyst.